zdump -v confusion

This is current/amd64.

The first two and last two lines of every zdump -v output
seem to include NULL values, as in

$ zdump -v Europe/Prague
Europe/Prague -9223372036854775808 = NULL
Europe/Prague -9223372036854689408 = NULL
Europe/Prague Mon Dec 31 23:02:15 1849 UTC = Mon Dec 31 23:59:59 1849 LMT isdst=0
Europe/Prague Mon Dec 31 23:02:16 1849 UTC = Tue Jan 1 00:00:00 1850 PMT isdst=0
[...]
Europe/Prague Sun Oct 25 00:59:59 2499 UTC = Sun Oct 25 02:59:59 2499 CEST isdst=1
Europe/Prague Sun Oct 25 01:00:00 2499 UTC = Sun Oct 25 02:00:00 2499 CET isdst=0
Europe/Prague 9223372036854689407 = NULL
Europe/Prague 9223372036854775807 = NULL

According to zdump(8), these must be

the time at the lowest possible time value,
the time one day after the lowest possible time value,
the time at one day less than the highest possible time value,
and the time at the highest possible time value.

Why are these times formated differently then the rest
(namely, an "%lld" of the time_t)?

Also, these seem to be a counterexample to

Each line ends with "isdst=1" if the given time is
Daylight Saving Time or "isdst=0" otherwise.